Défense de thèse de doctorat en Sciences physiques - Adrien NÉLIS
Study of germanium diffusion and nanoclustering in Si-based host matrices for optoelectronic applications such as third generation photovoltaic cells
Date : 28/09/2021 15:00 - 28/09/2021 18:00
Lieu : S01
Orateur(s) : Adrien NÉLIS
Organisateur(s) : Guy TERWAGNE
Jury
- Prof. Robert SPORKEN (département de physique, UNamur), président
- Prof. Guy TERWAGNE (département de physique, UNamur), secrétaire et promoteur
- Prof. Denis FLANDRE (pôle en ingénierie électrique, UCLouvain)
- Dr Ian VICKRIDGE (institut des nanosciences de Paris, Sorbonne Université)
- Prof. François SCHIETTEKATTE (département de physique, Université de Montréal)
- Prof. Olivier DEPARIS (département de physique, UNamur)
Abstract
The development of modern optoelectronic devices undoubtedly involves the study of the properties of materials at the nanoscale. In this context, the association of germanium and silicon quantum dots, incorporated in a dielectric film, offers new possibilities thanks to manyfold attractive optoelectronic properties. This is particularly the case in the field of photovoltaics for which quantum confinement, multiple exciton generation (MEG) or tunable bandgap are all properties that can make it possible to exceed the theoretical conversion limit of Shockley-Queisser calculated for a single-junction cell.
This purely experimental thesis aims to propose solutions to precisely control the formation of germanium quantum dots (location, size, distribution) in SiO2/Si films. The results presented in this thesis are based on the characterization of thin films via the combination of several analysis techniques, ranging from ion beam analysis to analysis by optical spectroscopies, including electronic microscopy. In particular, it has been shown that it was possible to completely annihilate the diffusion of germanium, occurring during post-implantation annealing, by judiciously generating a local excess of silicon by co-implantation, the affinity of germanium with silicon playing a preponderant role in the trapping effects highlighted in this thesis. It has been demonstrated that this singular relation between Ge and Si could allow controlling the position and the size distribution of the Ge quantum dots. The mechanisms responsible for the diffusion of germanium have been brought to light, with special attention to the involvement of oxygen in the redistribution of germanium atoms during thermal treatments.
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